Hilary Mantel, pictured at the Edinburgh international book festival in 2009. Photograph: Colin McPherson

Thomas Cromwell will play no part in Hilary Mantel's next book, to the inevitable disappointment of readers avidly awaiting The Mirror and the Light, the promised finale of her majestic trilogy of historical novels.

Instead 4th Estate has announced The Assassination of Margaret Thatcher, a collection of contemporary short stories to be published next autumn, simultaneously in the UK and by HarperCollins Canada and Henry Holt in the US.

Nicholas Pearson, publishing director of 4th Estate, promised: "A new book from Hilary Mantel is a treat.

"Where her last two novels explore how modern England was forged, The Assassination of Margaret Thatcher shows us the country we have become. These stories are Mantel at her observant best."

Mantel, the first woman to win the Booker prize twice, for Wolf Hall and then again for the second instalment of the Tudor saga, Bring Up the Bodies – which also won the Costa book of the year award – has published 13 books, but has not released a short story collection since Learning to Talk, in 2003.

She intends to finish the third Cromwell volume this year, and has said she is already anxious about the pressure of expectation that she will win the Booker again.

It will open, she recently revealed, with Cromwell on the scaffold, moments after the execution of Anne Boleyn.

She was excoriated last year for a speech at the British Museum dealing with the media perception of royal women, in which she described Kate Middleton as "selected for her role of princess because she was irreproachable: as painfully thin as anyone could wish, without quirks, without oddities, without the risk of the emergence of character".